The joint European-Japanese EarthCARE satellite began its mission to improve our understanding of Earth’s climate on Tuesday with a launch aboard a SpaceX Falcon 9 rocket. Liftoff from Space Launch Complex 4E (SLC-4E) at Vandenberg Space Force Base in California took place at 3:20 p.m. Pacific Time ( 22:20 UTC).
Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) is a joint project between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) and the sixth Earth Explorer mission to be launched under ESA’s Living Planet Programme. A satellite that was also named Hakuryu — or white dragon — from JAXA, carries four instruments that will study clouds and aerosols — fine particles and liquid droplets suspended in Earth’s atmosphere — and how they affect the planet’s climate.
By bringing together a suite of different instruments on one satellite, EarthCARE will be able to make different types of measurements that will complement each other, giving scientists a better understanding of how clouds and atmospheric aerosols interact with solar radiation and how it affects solar radiation. the planet’s radiation balance – the difference between the energy the Earth receives from the Sun and the energy it emits into space.
Scientists have long known that clouds affect Earth’s radiation balance, both by reflecting sunlight back into space and by absorbing heat that would otherwise be radiated into space. The height and structure of the cloud, its water content, and the presence of different types of aerosol can change the way it interacts with this system. By creating a complete picture of the internal structure of clouds, EarthCARE will help improve the models used to predict changes in Earth’s climate.
The 2,200 kg EarthCARE satellite was developed by a multinational consortium with Airbus Defense and Space as the main contractor. Power for the mission will be generated by a single deployable solar array that is 11 m long. The satellite is expected to operate for at least three years in a circular sun-synchronous orbit at an altitude of 393 km and an inclination of 97 degrees.
Development of the satellite began in 2008 with the signing of a contract between ESA and Astrium Satellites, which became part of Airbus in 2013. The four instruments were manufactured separately before being sent to integrate with the rest of the spacecraft. Testing was conducted at the European Space Research and Technology Center in the Netherlands before final checks at the Airbus facility in Friedrichshafen, Germany. In March 2024, the satellite was sent to the launch site.
The four EarthCARE instruments consist of an Atmospheric LIDAR (ATLID), a Cloud Profiling Radar (CPR), a Multispectral Imager (MSI) and a Broadband Radiometer (BBR). Atmospheric LIDAR (detection and ranging) is used to measure the altitudes of clouds and aerosols. The instrument uses a laser that emits 26-nanosecond ultraviolet pulses with a wavelength of 355 nm, and a 62 cm telescope as a receiver. The pulses from the laser will be transmitted into the atmosphere, where they will be scattered by particles and water molecules. Some of this is reflected back to the receiver, with the orbital period used to calculate the altitude at which the scattering occurred. Comparing the wavelength of the scattered light with that of the emitted light will also help determine the type of scattering that occurred, and therefore infer the type of particle that caused it to scatter.
The ATLID instrument on board EarthCARE was manufactured by Airbus and weighs about 500 kg.
CPR will allow EarthCARE to penetrate clouds and collect data on their vertical structure. The instrument is a major part of JAXA’s contribution to the mission and was built by Japan’s NEC Corporation. CPR will use a millimeter-wave Doppler radar that will emit 3.3-microsecond pulses at a frequency of 94 GHz into the atmosphere. Signals that are backscattered are received using the device’s 2.5m antenna. Studying how the signal has been Doppler-shifted will make it possible to determine the internal structure of the clouds and also make it possible to measure the vertical movement of the cloud and elements of its structure.
WE WILL LAUNCH SOON🚀🛰️
The #TAKE care of the Earth the satellite carries four cloud and aerosol observation instruments with four synergistic sensing methodologies.
The instruments provide key measurements to answer critical scientific questions related to the role that clouds and… pic.twitter.com/4GqCnoNRve
— ESA Earth Observation (@ESA_EO) May 26, 2024
Built by Thales in the UK, the BBR consists of three telescopes measuring the flux of radiation detected from Earth. One of its telescopes points in the nadir direction—that is, straight down toward Earth—while the others focus on points along the satellite’s path that are in front of and behind its current position. This allows the same point to be observed from three different angles as the satellite moves through its orbit.
Each telescope has one mirror and a linear sensor. The helicopter’s rotating drum alternates the telescope’s view between unfiltered light, a filter that lets only shortwave radiation through, and a constant-temperature surface that helps maintain calibration.
The shortwave filter limits the BBR measurement to only radiation from the Sun that has been reflected by the Earth. Subtracting this value from the total value without the filter will make it possible to calculate the amount of long-wave radiation emitted by the Earth itself. These data are important for monitoring the radiation balance of the planet.
The MSI is an imaging system consisting of two separate cameras with a common electrical and control segment, developed by Surrey Satellite Technology Ltd in the UK. The thermal infrared camera operates in three different wavelength channels, while the second camera produces images in the visible, near-infrared and two short-wave infrared channels. The MSI observations support data from other EarthCARE instruments by providing context to the data collected by ATLID and CPR and the spectral data that help calibrate the BBR measurements. MSI has a resolution of up to 500 m and covers a 150 km strip of the earth’s surface.
The EarthCARE satellite pictured being removed from its shipping container upon arrival at Vandenberg. (Credit: ESA)
EarthCARE will be launched by SpaceX aboard a Falcon 9 rocket, a two-stage vehicle consisting of a reusable booster and an expendable second stage. The launch will take place from Space Launch Complex 4E (SLC-4E) at Vandenberg Space Force Base in California.
The booster that was used for the EarthCARE mission is B1081.7, which made its seventh flight with this launch. B1081 first flew on August 26, 2023, carrying Dragon Perseverance on the Crew-7 mission to the International Space Station, following up on the CRS-29 Cargo Dragon mission in November. After launching the Starlink group of satellites in December, its fourth launch put NASA’s PACE satellite into orbit in February. B1081 was further used for the joint launch of Transporter-10 in March, which marked its first launch from Vandenberg, before its final mission, another Starlink launch, on 7 April.
ESA originally selected a Soyuz rocket for the EarthCARE deployment, with Arianespace carrying out the launch from the Center Spatial Guyanais in Kourou, French Guiana. After the Russian invasion of Ukraine in 2022, Arianespace’s partnership with Russia in performing Soyuz launches ended and the launch was moved to the new Vega-C rocket. This was then changed back to the Falcon 9 in 2023, a decision that was made both due to delays following the failed Vega-C launch in December 2022 and the modifications that would be required to its payload fairing to fit into the EarthCARE satellite entered.
The Falcon 9 flew in a return-to-launch-site (RTLS) profile, with the first stage successfully returning to land at Landing Zone 4 (LZ-4) near the launch pad after completing its role in Tuesday’s mission. The ability to recover and reuse the first stage has contributed significantly to the Falcon 9’s success: since its first flight in June 2010, it has already established itself as one of the most flown rockets ever produced. By some metrics, EarthCARE will mark the 350th flight or mission of the Falcon 9 and Falcon Heavy family: the first if the suborbital Crew Dragon In-Flight Abort (IFA) test in 2020 is included in the count; and the last if the 2016 Amos 6 mission is included instead, in which the rocket exploded on the launch pad during preparations for a static fire test two days before the scheduled launch.
Despite its high flight speed, the Falcon 9 has also proven to be one of the most reliable rockets in service. Apart from Amos 6, it has so far suffered only one in-flight failure and one other partial failure, and since Amos 6 has made 320 consecutive successful launches via Falcon 9 and Falcon Heavy vehicles – the latter using two additional boosters burning in parallel. with a first stage that will allow it to carry a heavier payload to a higher orbit.
Render of the second stage of Falcon 9 and EarthCARE during fairing separation. (Credit: ESA/P. Carril)
For Tuesday’s mission, a single-core Falcon 9 will be enough to put EarthCARE into its planned sun-synchronous orbit, with enough power left over to return the booster to its launch site. Falcon 9 uses RP-1 kerosene with liquid oxygen (LOX) as an oxidizer. Propellant and LOX loading occurs during the final 35-minute countdown, with the nine Merlin-1D first-stage engines igniting about three seconds before the scheduled liftoff time, or T0. After takeoff, the Falcon will fly down in a southerly direction.
The first stage will power the ascent for about two and a half minutes before it shuts down, separates, and begins flight back to LZ-4. The second stage will ignite its Merlin vacuum engine – a version of the Merlin optimized for use in space – and continue the mission. Shortly thereafter, the payload fairing separates from EarthCARE’s surroundings at the nose of the rocket. The second stage will burn for just over six minutes to reach EarthCARE’s planned orbit, with spacecraft separation occurring about ten minutes after liftoff.
After separation from Falcon 9, EarthCARE will need to deploy its solar array and other key systems and begin in-orbit testing and commissioning before it can enter service.
(Feature image: Falcon 9 B1081-7 time-lapse image of EarthCARE launch from Vandenberg Space Force Base. Credit: Pauline Acalin for NSF)